Preheat the oven to 250 degrees F. Line two large rimmed cookie sheets (or roasting pans if that's all you've got) with parchment paper. If you are making half, you can use one cookie sheet. Don't try putting it all on one cookie sheet or it won't cook properly.
In a large bowl, stir together the rolled oats, almonds, pecans, coconut and sunflower seeds. Toss in salt and stir to evenly disperse salt.
In a microwave-safe measuring cup, stir together the brown sugar, maple syrup, honey and vegetable oil. Heat on high for 1 minute, then stir to dissolve sugar slightly. Stir in vanilla. Pour hot syrup mixture over granola and stir until evenly coated. Dump oat mixture out onto the two cookie sheets, spreading as evenly as possible and pressing down slightly so that oats are in a thin, closely packed layer
Cover loosely with large pieces of foil. Bake for 1 hour, 1 pan on lower rack and one on upper. When you smell the granola (after about 40 minutes), check it to make sure it's not browning too much. If it's covered, it should be fine. Also, the granola on the lower rack will cook quickly, so after 40 minutes, swap racks. After 1 hour, remove the foil. Cook for another 15 minutes or until it is golden brown. Remove from oven and let cool completely. Granola will crisp as it cools, so don't worry if all of the granola doesn't seem crisp after 1 hour and 15 minutes. When cool, break the bigger clumps up into smaller clumps.
Note: You may want to try this first with half a batch baked on middle rack of oven. When baking two pans, you run the risk of burning the pan on the bottom rack, so if you are doing two pans, watch bottom pan closely and swap spaces.